Potassium hypochromate
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Names | |
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Other names
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3D model (JSmol) |
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Properties | |
Chemical formula | K3CrO4 |
Molar mass | 233.2886 g/mol |
Appearance | Green solid |
Melting point | 1,000 °C (1,830 °F; 1,270 K) (decomposes) |
Solubility in water | Soluble, decomposes (25 °C)[1] |
Structure | |
Crystal structure | Similar to potassium hypomanganate |
Thermochemistry | |
Std enthalpy of formation (ΔfH⦵298) | -370 ± 2 kcal mol−1[2] |
Hazards | |
Flash point | Not flammable |
Related compounds | |
Other anions | Potassium hypomanganate |
Other cations | Sodium hypochromate |
Related chromates | Potassium chromate Potassium perchromate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references |
Potassium hypochromate is a chemical compound with the formula K3CrO4 with the unusual Cr5+ ion. This compound is unstable in water but stable in alkaline solution[1] and was found to have a similar crystal structure to potassium hypomanganate.[2]
Preparation
This compound is commonly prepared by reacting chromium(III) oxide and potassium hydroxide at 850 °C under argon:[2]
- Cr2O3 + 6 KOH → 2 K3CrO4 + H2O + 2 H2
This compound can be prepared other ways such as replacing chromium oxide with potassium chromate. It is important that there is no Fe2+ ions present because it would reduce the Cr(V) ions to Cr(III) ions.[1]
Reactions
Potassium hypochromate decomposes in water to form chromium(III) oxide and potassium chromate when alkali is not present or low.[1] Potassium hypochromate also reacts with acids such as hydrochloric acid to form chromium(III) oxide, potassium chromate, and potassium chloride:[2]
- 6 K3CrO4 + 10 HCl → 4 K2CrO4 + Cr2O3 + 5 H2O + 10 KCl
Other reducing agents such as hydroperoxides can oxidize the hypochromate ion into chromate ions.[1] At extremely high temperatures, it decomposes into potassium chromate and potassium metal.[2]
This compound is used to synthesize various compounds such as chromyl chlorosulfate by reacting this compound with chlorosulfuric acid.[3]
References
- ^ a b c d e N. Bailey; M. C. R. Symons (1957). "Structure and reactivity of the oxyanions of transition metals. Part III. The hypochromate ion". Journal of the Chemical Society (Resumed). 35: 203–207. doi:10.1039/jr9570000203.
- ^ a b c d e Lawrence H. Johnson; Loren G. Hepler; Carlos E. Bamberger; Donald M. Richardson (1978). "The enthalpy of formation of potassium chromate(V), K3CrO4(c)". Canadian Journal of Chemistry. 56 (4). The Ohio State University: National Research Council: 446–449. doi:10.1139/v78-071.
- ^ Silvia A. Brandán (2012). "1". A Structural and Vibrational Study of the Chromyl Chlorosulfate, Fluorosulfate, and Nitrate Compounds (Ebook). Springer Netherlands. p. 2. ISBN 9789400757639. Retrieved 15 October 2021.
- v
- t
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- K3N
- KNH2
- KN3
- KNO2
- KNO3
- K3P
- KH2PO3
- K3PO4
- K2HPO4
- KH2PO4
- KPF6
- KAsO2
- K3AsO4
- K2HAsO4
- KH2AsO4
- B4K2O7
- K2CO3
- KHCO3
- K2SiO3
- K2SiF6
- K2Al2O4
- K2Al2B2O7
- K2PtCl4
- K2Pt(CN)4
- K2TiF6
- K2PtCl6
- K2ReCl6
- KAsF6
- K2ReBr6
- K2ZrF6
- K4Fe(CN)6
- K3Fe(CN)6
- K3Fe(C2O4)3
- K2FeO4
- K2MnO4
- KMnO4
- K3CrO4
- K2CrO4
- K3CrO8
- KCrO3Cl
- K2Cr2O7
- K2Cr3O10
- K2Cr4O13
- K4Mo2Cl8
- KHCO2
- KCH3CO2
- KCF3CO2
- K2C2O4
- KHC2O4
- KC12H23O2
- KC18H35O2
- C3H2K2O4
- C4H6KO4
- C5H7KO4